diff mbox series

[v7,04/24] x86/resctrl: Move rmid allocation out of mkdir_rdt_prepare()

Message ID 20231025180345.28061-5-james.morse@arm.com
State New
Headers
Series x86/resctrl: monitored closid+rmid together, separate arch/fs locking |

Commit Message

James Morse Oct. 25, 2023, 6:03 p.m. UTC 
  RMID are allocated for each monitor or control group directory, because
each of these needs its own RMID. For control groups,
rdtgroup_mkdir_ctrl_mon() later goes on to allocate the CLOSID.

MPAM's equivalent of RMID is not an independent number, so can't be
allocated until the CLOSID is known. An RMID allocation for one CLOSID
may fail, whereas another may succeed depending on how many monitor
groups a control group has.

The RMID allocation needs to move to be after the CLOSID has been
allocated.

Move the RMID allocation out of mkdir_rdt_prepare() to occur in its caller,
after the mkdir_rdt_prepare() call. This allows the RMID allocator to
know the CLOSID.

Tested-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
Tested-by: Peter Newman <peternewman@google.com>
Reviewed-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: James Morse <james.morse@arm.com>
---
Changes since v2:
 * Moved kernfs_activate() later to preserve atomicity of files being visible

Changes since v5:
 * Renamed out_id_free as out_closid_free.

No changes since v6
---
 arch/x86/kernel/cpu/resctrl/rdtgroup.c | 35 +++++++++++++++++++-------
 1 file changed, 26 insertions(+), 9 deletions(-)

Comments

Moger, Babu Nov. 9, 2023, 8:29 p.m. UTC | #1 
Hi James,

On 10/25/23 13:03, James Morse wrote:
> RMID are allocated for each monitor or control group directory, because
> each of these needs its own RMID. For control groups,
> rdtgroup_mkdir_ctrl_mon() later goes on to allocate the CLOSID.
> 
> MPAM's equivalent of RMID is not an independent number, so can't be
> allocated until the CLOSID is known. An RMID allocation for one CLOSID
> may fail, whereas another may succeed depending on how many monitor
> groups a control group has.
> 
> The RMID allocation needs to move to be after the CLOSID has been
> allocated.
> 
> Move the RMID allocation out of mkdir_rdt_prepare() to occur in its caller,
> after the mkdir_rdt_prepare() call. This allows the RMID allocator to
> know the CLOSID.
> 
> Tested-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
> Tested-by: Peter Newman <peternewman@google.com>
> Reviewed-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
> Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
> Signed-off-by: James Morse <james.morse@arm.com>
> ---
> Changes since v2:
>  * Moved kernfs_activate() later to preserve atomicity of files being visible
> 
> Changes since v5:
>  * Renamed out_id_free as out_closid_free.
> 
> No changes since v6
> ---
>  arch/x86/kernel/cpu/resctrl/rdtgroup.c | 35 +++++++++++++++++++-------
>  1 file changed, 26 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 1eb3a3075093..8fb0f56f64be 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -3317,6 +3317,12 @@ static int mkdir_rdt_prepare_rmid_alloc(struct rdtgroup *rdtgrp)
>  	return 0;
>  }
>  
> +static void mkdir_rdt_prepare_rmid_free(struct rdtgroup *rgrp)
> +{
> +	if (rdt_mon_capable)
> +		free_rmid(rgrp->mon.rmid);
> +}

The check if (rdt_mon_capable) is extra here. Not required. Otherwise
looks good.

Reviewed-by: Babu Moger <babu.moger@amd.com>
James Morse Dec. 13, 2023, 6:03 p.m. UTC | #2 
Hi Babu,

On 09/11/2023 20:29, Moger, Babu wrote:
> On 10/25/23 13:03, James Morse wrote:
>> RMID are allocated for each monitor or control group directory, because
>> each of these needs its own RMID. For control groups,
>> rdtgroup_mkdir_ctrl_mon() later goes on to allocate the CLOSID.
>>
>> MPAM's equivalent of RMID is not an independent number, so can't be
>> allocated until the CLOSID is known. An RMID allocation for one CLOSID
>> may fail, whereas another may succeed depending on how many monitor
>> groups a control group has.
>>
>> The RMID allocation needs to move to be after the CLOSID has been
>> allocated.
>>
>> Move the RMID allocation out of mkdir_rdt_prepare() to occur in its caller,
>> after the mkdir_rdt_prepare() call. This allows the RMID allocator to
>> know the CLOSID.

>> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> index 1eb3a3075093..8fb0f56f64be 100644
>> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> @@ -3317,6 +3317,12 @@ static int mkdir_rdt_prepare_rmid_alloc(struct rdtgroup *rdtgrp)
>>  	return 0;
>>  }
>>  
>> +static void mkdir_rdt_prepare_rmid_free(struct rdtgroup *rgrp)
>> +{
>> +	if (rdt_mon_capable)
>> +		free_rmid(rgrp->mon.rmid);
>> +}
> 
> The check if (rdt_mon_capable) is extra here. Not required. Otherwise
> looks good.

It pairs with the behaviour of mkdir_rdt_prepare_rmid_alloc(), which returns early if
(!rdt_mon_capable). This avoids double-adding rmid-0 to the limbo list.


> Reviewed-by: Babu Moger <babu.moger@amd.com>

Thanks! I assume you're happy with my above description of the rdt_mon_capable check is
needed.


Thanks,

James
diff mbox series

Patch

diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 1eb3a3075093..8fb0f56f64be 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -3317,6 +3317,12 @@  static int mkdir_rdt_prepare_rmid_alloc(struct rdtgroup *rdtgrp)
 	return 0;
 }
 
+static void mkdir_rdt_prepare_rmid_free(struct rdtgroup *rgrp)
+{
+	if (rdt_mon_capable)
+		free_rmid(rgrp->mon.rmid);
+}
+
 static int mkdir_rdt_prepare(struct kernfs_node *parent_kn,
 			     const char *name, umode_t mode,
 			     enum rdt_group_type rtype, struct rdtgroup **r)
@@ -3389,12 +3395,6 @@  static int mkdir_rdt_prepare(struct kernfs_node *parent_kn,
 		goto out_destroy;
 	}
 
-	ret = mkdir_rdt_prepare_rmid_alloc(rdtgrp);
-	if (ret)
-		goto out_destroy;
-
-	kernfs_activate(kn);
-
 	/*
 	 * The caller unlocks the parent_kn upon success.
 	 */
@@ -3413,7 +3413,6 @@  static int mkdir_rdt_prepare(struct kernfs_node *parent_kn,
 static void mkdir_rdt_prepare_clean(struct rdtgroup *rgrp)
 {
 	kernfs_remove(rgrp->kn);
-	free_rmid(rgrp->mon.rmid);
 	rdtgroup_remove(rgrp);
 }
 
@@ -3435,12 +3434,21 @@  static int rdtgroup_mkdir_mon(struct kernfs_node *parent_kn,
 	prgrp = rdtgrp->mon.parent;
 	rdtgrp->closid = prgrp->closid;
 
+	ret = mkdir_rdt_prepare_rmid_alloc(rdtgrp);
+	if (ret) {
+		mkdir_rdt_prepare_clean(rdtgrp);
+		goto out_unlock;
+	}
+
+	kernfs_activate(rdtgrp->kn);
+
 	/*
 	 * Add the rdtgrp to the list of rdtgrps the parent
 	 * ctrl_mon group has to track.
 	 */
 	list_add_tail(&rdtgrp->mon.crdtgrp_list, &prgrp->mon.crdtgrp_list);
 
+out_unlock:
 	rdtgroup_kn_unlock(parent_kn);
 	return ret;
 }
@@ -3471,9 +3479,16 @@  static int rdtgroup_mkdir_ctrl_mon(struct kernfs_node *parent_kn,
 	ret = 0;
 
 	rdtgrp->closid = closid;
+
+	ret = mkdir_rdt_prepare_rmid_alloc(rdtgrp);
+	if (ret)
+		goto out_closid_free;
+
+	kernfs_activate(rdtgrp->kn);
+
 	ret = rdtgroup_init_alloc(rdtgrp);
 	if (ret < 0)
-		goto out_id_free;
+		goto out_rmid_free;
 
 	list_add(&rdtgrp->rdtgroup_list, &rdt_all_groups);
 
@@ -3493,7 +3508,9 @@  static int rdtgroup_mkdir_ctrl_mon(struct kernfs_node *parent_kn,
 
 out_del_list:
 	list_del(&rdtgrp->rdtgroup_list);
-out_id_free:
+out_rmid_free:
+	mkdir_rdt_prepare_rmid_free(rdtgrp);
+out_closid_free:
 	closid_free(closid);
 out_common_fail:
 	mkdir_rdt_prepare_clean(rdtgrp);